From what I've read the procedure usually is a bit shorter than a traditional TKR approach where the incision is down the front of the knee. To me, that's likely one of the reasons there can be better results with post-op pain levels. The more time spent in surgery, the more likely a patient is to have pain as there is more trauma to the soft tissue. Less time equals less tissue trauma.
I think what EalingGran was referring to by being "more complex" is that the technique for the surgery can require more surgical skill
because there are fewer cuts made and instead more tissue is pulled to the side. This technique, while better for the patient, would require the surgeon to take additional care so as not to overly stretch the tissues as the surgery proceeds. This can make things more complex. In addition, the complexity of the surgery also comes from the fact that the surgeon does not have as much free access to the knee joint. Just as with an anterior hip approach, the lateral subvastus knee procedure requires the surgeon to work in a more confined area.
If you look at the Jiffy Knee website, you'll see there are still a few small cuts that are made, but it definitely is less trauma on the knee. These minor cuts are then sutured together and should heal fairly quickly with reduced pain levels compared to having to tease the muscles apart as part of a traditional procedure. This teasing of muscles is routine now in knee replacements instead of the older technique of actually cutting the quad muscle. But it still does involve more trauma to the soft tissue than the lateral subvastus approach.
There have been a few promising studies written on the lateral subvastus approach. This is a technique that has promise and may become the norm as more surgeons are made aware and trained in the procedure. For now, it will be good to have your experience documented for others to see how this worked for you.